
//修正uv
vec2 fixUV(in vec2 coord){
  vec2 p ;
  p.x = 2.*coord.x/iResolution.x-1.;
  p.y=2.*coord.y/iResolution.y-1.;
  return p;
}

float sdCircle( in vec2 p, in float r ) 
{
    return length(p)-r;
}


void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
	vec2 p = fixUV(fragCoord);

	//  vec2 p = fragCoord;
  float t= abs(cos(iTime));
	float d = sdCircle(p,t);
    
	// coloring

float v  = smoothstep (0.,1.,d);

vec3 col = vec3(v,v,v) ;
col *= cos(1000.*cos(iTime)*d);
	fragColor = vec4(col,1.0);
}